Systems for applying energy to biological tissue are well known. Such energy application may be intended to heal injured tissue, ablate tissue, or improve the appearance of tissue. Energy may be applied in different forms, such as radiofrequency, laser, or ultrasound.
PCT Publication WO 06/080012 to Kreindel, which is incorporated herein by reference, describes a system and method for heating a tissue volume under a skin surface of an individual from an initial temperature to a predetermined treatment temperature in the range of 42 C-60 C. The method is described as comprising applying electrodes to the skin surface and providing from the electrodes a continuous wave radiofrequency (RF) energy or a quasi-continuous wave RF energy, where the RF energy has a power selected to heat the tissue volume to the final temperature in an amount of time exceeding 0.5 sec. The system is described as comprising electrodes and an RF generator configured to provide a continuous wave RF voltage energy or a quasi-continuous wave RF voltage across the electrodes where the RF energy has a power selected to heat the tissue volume to the final temperature in an amount of time exceeding 0.5 sec.
US Patent Application Publication 2004/0039312 to Hillstead et al., which is incorporated herein by reference, describes a system for the destruction of adipose tissue utilizing high intensity focused ultrasound (HIFU) within a patient's body. The system is described as comprising a controller for data storage and the operation and control of a plurality of elements. One element is described as a means for mapping a human body to establish three dimensional coordinate position data for existing adipose tissue. The controller is able to identify the plurality of adipose tissue locations on said human body and establish a protocol for the destruction of the adipose tissue. A HIFU transducer assembly having one or more piezoelectric element(s) is used along with at least one sensor, wherein the sensor provides feedback information to the controller for the safe operation of the piezoelectric element(s). The sensor is electronically coupled to the controller, and the controller provides essential treatment command information to one or more piezoelectric element(s) based on positioning information obtained from the three dimensional coordinate position data.
U.S. Pat. No. 6,500,141 to Irion et al., which is incorporated herein by reference, describes an apparatus for treating body tissue, in particular superficial soft tissue, with ultrasound, comprising an ultrasonic generation unit and an applicator, by means of which the ultrasound can be irradiated from an applicator surface facing the body surface from outside through the body surface into the body tissue. A suction apparatus for sucking in the body surface against the applicator surface is provided. An apparatus for treating body tissue including superficial soft tissue, with ultrasound, is described as comprising an ultrasonic generation unit and an applicator having an applicator surface facing the body surface from which the ultrasound can be irradiated through the body surface into the body tissue. A suction apparatus is provided for taking in the body surface against the applicator surface which is curved inwardly.
U.S. Pat. No. 5,601,526 to Chapelon et al., which is incorporated herein by reference, describes a method and apparatus for performing therapy using ultrasound. The apparatus is described as using a treatment device having at least one piezoelectric transducer element to supply ultrasonic waves focused onto a focal point or region that determines the tissue zone submitted to therapy. The treatment device, which is controlled by a control device, supplies two types of ultrasonic waves, the first one being thermal waves that produce a predominantly thermal effect on the tissue being treated and the second one being cavitation waves that produce a predominantly cavitation effect on the tissue to be treated. A therapy method is described, using ultrasound for the purpose of destroying a target. The target includes tissue, which may be located inside a body of a mammal. Ultrasonic waves are focused onto a focal point or region. A tissue zone to be submitted to the therapy is determined. Ultrasonic waves are supplied to the target. The ultrasonic waves of two types: thermal waves, for producing a predominantly thermal effect on tissue to be treated, and cavitation waves, for producing a predominantly cavitation effect on the tissue to be treated. The two types of waves are applied for a time sufficient to effect therapy by destroying at least a portion of the tissue, and the thermal ultrasonic waves are supplied at least at a beginning of treatment. In an embodiment, the ultrasonic waves are supplied after an adjustable predetermined time interval for allowing preheating of the tissue to be treated.
PCT Publication WO 06/018837 to Azhari et al., which is incorporated herein by reference, describes a method of damaging a target tissue of a subject. The method is described as comprising: (a) imaging a region containing the target tissue; (b) determining a focal region of a damaging radiation; (c) positioning the focal region onto the target tissue; and (d) damaging the target tissue by an effective amount of the damaging radiation. The determination of the focal region is described by delivering to the region bursts of ultrasonic radiation from a plurality of directions and at a plurality of different frequencies, and passively scanning the region so as to receive from the region ultrasonic radiation having at least one frequency other than the plurality of different frequencies.
US Patent Application Publications 2005/0154308, 2005/0154309, 2005/0193451, 2004/0217675, 2005/0154295, 2005/0154313, 2005/0154314, 2005/0154431, 2005/0187463, 2005/0187495, 2006/0122509, 2003/0083536, 2005/0261584, 2004/0215110, 2006/0036300, 2002/0193831, and 2006/0094988, U.S. Pat. Nos. 5,143,063, 6,730,034, 6,450,979, 6,113,558, 6,607,498, 6,626,854, 6,645,162, and 6,971,994, and PCT Patent Publications WO/2000/053263, and WO/2005/074365 are incorporated herein by reference.
The following articles, which are incorporated herein by reference, may be of interest:    Moran C M et al., “Ultrasonic propagation properties of excised human skin,” Ultrasound Med Biol. 21(9):1177-90 (1995)    Akashi N et al., “Acoustic properties of selected bovine tissue in the frequency range 20-200 MHz,” J Acoust Soc Am. 98(6):3035-9 (1995)